Brih Upanishad:~Yoga does not yield truth or liberation.+

The yogi may get the knowledge that the Seer is separate from Seen, but he will never know Brahman without inquiring into the world, because he is giving up the world, and hence cannot discover his unity with the world.  A Gnani regards everything in the world as Brahman; the yogi rejects the world. Thus there is a fundamental difference.

The phenomenal world, objective experience, other Seer, self, knower before one has obtained the power of control and consequently to banish the thoughts. This fact that Samadhi is deep sleep is kept secret because people would not be tempted to take up yoga.

What is the value of yoga?  It is only to sharpen the intellect, to enable it to keep away all extraneous thoughts when one gets out to reason in the practice of the next higher stage, i.e. Gnana.

Yoga is thus simply a sharpening-stone for the mindset to enable it to take up Gnana. Yogis claim that they live without thoughts but it is impossible to remain without the thoughts. How can yogi walk from one spot to another without thought? Yogis do not know the Gnanic truth because yogis think thoughtlessness is the perfect stage of ‘Self’.

What happens when thoughts are stilled? It is not the Self that is found. Rubbish. It is only the mind. Patanjali has not reached Gnana and therefore does not know the Advaitic truth. Patanjali yoga is good to give peace and concentration, but only in order to start reasoning, i.e. thinking again to find the truth.

If one thinks its mere disappearance in yogic Samadhi is the ultimate truth or Brahman, then he would get it in a deep sleep.  Thus, the yogic Samadhi is not the Advaitic wisdom. Thoughtlessness is not Advaitic wisdom.

Remember:~

Thoughtlessness is not wisdom. The thinker thought and the world are part of the illusion. The thought will not arise without the form, time and space. The form, time and space will not arise without the mind. 

The mind ceases to exist without the Soul which is in the form of the Spirit. Therefore, there is a need to know the “Self” is not limited to the physical entity (you), but it pervades in everything and everywhere in the experience of diversity (waking or dream). 

The deep sleep is the state of thoughtlessness, silence, wordlessness, silence but it is not considered as the state of oneness because anyone can take a sleeping pill and will be able to get a state of oneness. 

Thus, trying to imitate the state of oneness in duality by observing silence, thoughtlessness, wordlessness or by yogic Samadhi or surrendering to the physical Guru, the Advaitic wisdom will not dawn. Without the Advaitic wisdom, ignorance will not vanish. Thus, getting rid of ignorance through wisdom is the only way to realize the ultimate truth or Brahman.  

It is impossible to stop the thought for more than a half-second while in the waking state. If one succeeds in controlling thought and then banishes it, one passes into Nirvikalpa samadhi, identical to deep sleep. 

The only difference between ordinary deep sleep and samadhi, therefore, is that the ordinary man falls asleep involuntarily whereas the yogi has the satisfaction of knowing that he has passed into sleep by his own effort of will in banishing thoughts.

Remember:~

Brih Upanishad: page 32. "Yoga does not yield truth or liberation."

One who is in Samadhi will not know that this universe as the consciousness; therefore yoga is not the means to Self-knowledge or Brahma Gnana or Atma Gnana.

 In Samadhi the yogi knows nothing, and sees no universe; so if there is nothing but blankness. The blankness is not the Advaitic wisdom.

The yogi does not know the nature of the universe. If the universe is not seen in the Samadhi then there is no need to use the word Atman and Brahman.  The yogi is unaware of the truth, which is beyond the form, time and space. 

By shutting his eyes in Samadhi, the yogi does not know the universe, which confronts him. Hence the universe can't be known as the Soul or the consciousness through yoga.

One is in a non-dual condition in deep sleep or Samadhi, One without a second, true, but he did not know it at the time. He says only in the waking experience afterward. Hence, there must be an inquiry so that you find non-duality whilst you are awake so that you can see nonduality at the time not afterwards. Hence, too the need for inquiring into the nature of the universe and knowing it as the Soul or the consciousness whilst one is awake, and not during sleep or Samadhi.

Advaitic truth is the ultimate truth.  Yogis, mystics and religious teachers do not accept the path of wisdom because it pries into the truth, the source and the validity of the knowledge they claim. Therefore, it is the most difficult part of the study of Advaita. : ~ Santthosh Kumaar